Lanthanide Clusters Research Articles

Anion and Solvent Manipulated Out-to-In Growth Mechanism to Assemble a Series of Different Dysprosium Clusters

Abstract Although various lanthanide clusters with different shapes and connections have been synthesised, more rules are still needed to guide their further serial expansion and directed structural modification. Herein, we used the multidentate chelating ligand N′2,N′9-bis((E)-2-hydroxy-3-methoxybenzylidene)-1,10-phenanthroline-2,9-dicarbohydrazide (H4L) to react with Dy(NO3)3·6H2O under EtOH/CH3CN conditions to obtain an example of a nonanuclear dysprosium cluster, i.e., [Dy9(L)2(μ2-OH)(μ3-OH)6(NO3)12(H2O)3]·5CH3CN·H2O (1). The structural framework of cluster 1 contains 2 (L)4− ligands, 1 μ2-OH−, 6 μ3-OH−, 12 NO3−, and 3 H2O. Each ligand (L)4− chelates five Dy(III) ions, and its coordination mode is μ5-η1:η2:η1:η2:η1:η1:η2:η1:η2:η1. Cluster 1 has many different connection modes of NO3−, such as μ5-η2:η2:η2, μ2-η1:η1, and μ2-η1:η2. Notably, we only changed the metal salt to Dy(OAc)3·6H2O and obtained an example of a trinuclear dysprosium cluster, i.e., [Dy3(H2L)(OAc)7]·CH3CN·3H2O (2). The structure of cluster 2 contains three Dy(III) ions, one (H2L)2− ion, one μ3-η2:η2-bridged OAc− and six end-coordinated OAc−. The coordination mode of ligand (H2L)2− is μ3-η1:η1:η2:η1:η1:η1:η2:η1. More notably, we only changed the solvent to MeOH/CH3CN, and under the same reaction conditions, we got an example of a dodeca-nucleus dysprosium cluster, i.e., [Dy12(L)4(μ2-OH)2(OAc)14(H2O)8]·4C2H3O2·2H2O (3). In cluster 3, ligand (L)4− adopts the μ5-η1:η2:η1:η2:η1:η1:η2:η1:η2:η1 coordination mode, and the four ligands (L)4− are connected to each other forming the grid structure. Twelve Dy(III) ions are “embedded” in the chelating sites of the ligand and bridged by multiple OAc− ions. A large cavity is formed in the centre of the ‘well’ in cluster 3. The test results of variable temperature AC magnetic susceptibility show that clusters 1–3 all exhibit single-molecule magnet behaviour. To the best of our knowledge, this study is the first to describe that an out-to-in growth mechanism has been manipulated by anions and solvents to realise the synthesis of a series of completely differently connected dysprosium clusters. In addition, this mechanism is also one of the rare examples of anion and solvent co-induced assembly to form lanthanide clusters with completely different shapes and connections.

Structure, derivatisation, and metal complexation of p-cyclohexylcalix[4]arene

ABSTRACT Driven by an interest in the impact of the para-substituent of calix[4]arenes on metal complexation and structural chemistry, studies of p-cyclohexylcalix[4]arene (L) have been carried out. The 1:1 dichloromethane and dimethylformamide solvates were found to be isostructural, and different to the typical bilayer structure often observed for p-t-butylcalix[4]arene solvates. The methanol solvate, in contrast, does form a bilayered structure but is also a 1:1 solvate, unlike the p-t-butylcalix[4]arene·2MeOH system. Lanthanoid complexation was investigated, resulting in the structural characterisation of two different DMF solvates of a 2:2 dimeric europium complex, Eu2(L–3H)2(DMF)4. A tetrazole derivative, 5,11,17,23-tetracyclohexyl-25,27-dihydroxy-26,28-bis(tetrazole-5-ylmethoxy)calix[4]arene, has been synthesised via the intermediate 5,11,17,23-tetracyclohexyl-25,27-dihydroxy-26,28-dicyanomethoxycalix[4]arene, with the latter compound being structurally characterised. Attempts to isolate lanthanoid clusters supported by the tetrazole derivative under conditions known to form Ln19 clusters with the p-t-butyl analogue were unsuccessful, resulting only in isolation of the ligand from the reaction mixture.

Recent advances in lanthanide coordination polymers and clusters with magnetocaloric effect or single-molecule magnet behavior.

Molecular magnetorefrigerant materials for low-temperature magnetic refrigeration and single-molecule magnets for high-density information storage and quantum computing have received extensive attention from chemists and magnetic experts. Lanthanide ions with unique magnetic properties have always been considered as ideal candidates for the construction of such materials. This frontier article focuses on GdIII-based molecular magnetorefrigerants and lanthanide-based single-molecule magnets and highlights the most significant advances.

PH manipulates the assembly of a series of dysprosium clusters with subtle differences

This study is the first to fine-tune a series of lanthanide clusters with the same shape through pH manipulation.

Lanthanide clusters of phenanthroline containing a pyridine-pyrazole based ligand: magnetism and cell imaging.

In this contribution, we report the synthesis, characterization and luminescence-magnetic properties of Ln-clusters (Ln = Gd3+, Eu3+ and Tb3+) using a new pyridine-pyrazole functionalized ligand fitted with a chromophoric phenanthroline backbone. The unorthodox N-rich ligand forms isostructural trinuclear lanthanide complexes with a topology that closely resembles two interdigitating hairpins. The clusters crystallize in chiral space groups and also exhibit chirality for bulk samples, which were further confirmed using solid state CD spectra. Magnetic studies on the complexes reveal their interesting features while the Gd cluster shows a significant cryogenic magnetic cooling behaviour with a moderately high magnetic entropy change of -23.42 J kg-1 K-1 at 7 T and 2 K. On the other hand, Eu and Tb complexes exhibit interesting fluorescence properties. The compounds were subsequently used as fluorescent probes for the imaging of human breast adenocarcinoma (MCF7) cells. Live cell confocal microscopy images show that the complexes penetrate beyond the usual cytoplasm region and can be useful in imaging the nucleus region of MCF7 cells.

Asymmetric Ring Opening in a Tetrazine-Based Ligand Affords a Tetranuclear Opto-Magnetic Ytterbium Complex.

We report the formation of a tetranuclear lanthanide cluster, [Yb4 (bpzch)2 (fod)10 ] (1), which occurs from a serendipitous ring opening of the functionalised tetrazine bridging ligand, bpztz (3,6-dipyrazin-2-yl-1,2,4,5-tetrazine) upon reacting with Yb(fod)3 (fod- =6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octandionate). Compound 1 was structurally elucidated via single-crystal X-ray crystallography and subsequently magnetically and spectroscopically characterised to analyse its magnetisation dynamics and its luminescence behaviour. Computational studies validate the observed MJ energy levels attained by spectroscopy and provides a clearer picture of the slow relaxation of the magnetisation dynamics and relaxation pathways. These studies demonstrate that 1 acts as a single-molecule magnet (SMM) under an applied magnetic field in which the relaxation occurs via a combination of Raman, direct, and quantum tunnelling processes, a behaviour further rationalised analysing the luminescent properties. This marks the first lanthanide-containing molecule that forms by means of an asymmetric tetrazine decomposition.

A cocrystallization of polyoxotitanium cages with lanthanide clusters

Present herein is a new structure type of lanthanide-doped polyoxotitanium (Ln-POT) involving the separation of the polyoxotitanium and lanthanide clusters. A unique cocrystallization is observed in the structure of H6[Ti12(OiPr)18(μ3-O14)][La3(NO3)11(OiPr)6] (1). Diffuse reflectance spectroscopy showing lanthanide doping is shown to give favorable light absorption properties.

Two polyoxometalate-based hybrids constructed from trinuclear lanthanoid clusters with single‐molecule magnet behavior

In this paper we report the successful hydrothermal synthesis of the two inorganic–organic hybrid assemblies H0.87{Na(H2O)3[Dy(PDA)(H2O)2]3(BW12O40)0.87(SiW12O40)0.13}•11H2O (1) and H0.87{Na(H2O)3[Ho(PDA)(H2O)2]3 (BW12O40) 0.87(SiW12O40)0.13}•10H2O (2) (H2PDA = 1,10-phenanthroline-2,9-dicarboxylic acid). Both hybrids have been characterized using elemental analyses, Fourier transform infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Structural characterizations by single-crystal X-ray diffraction reveals that these hybrids are isostructural including [BW12O40]5- Keggin-type polyoxometalates (actually containing 87% B and 13% Si based on refinement of the crystal structures) connected by three lanthanoids to yield discrete trinuclear lanthanoid clusters. These discrete molecules are further packed into 3D supramolecular assemblies by means of hydrogen-bonding and anion–π interactions. 1 and 2 are two examples of a relatively small number of inorganic–organic hybrid POMs containing the PDA ligand based on a CSD search (CSD version 5.40 updated to November 2018). The temperature dependences of χmT for 1 and 2 are considered. Magnetic studies reveal that 1 exhibits typical single‐molecule magnet (SMM) behavior.

Hierarchical clusters of lanthanide cluster plus gold cluster

In this work, we provide a facile and valid one-pot synthesis method to create unreported hierarchical cluster of lanthanide cluster plus gold cluster (Ln-Au cluster), by introducing the ligands with bifunctional groups of carboxyl and sulfhydryl. The identities of Ln-Au clusters are fully characterized to be Ln7Au20 (MPCA)21 (Ln = Ce, 1; Eu, 2; Tb, 3; MPCA = 2-mercaptonicotinic acid) and Ln5Au18(TSA)15 (Ln = Ce, 4; Eu, 5; Tb, 6; TSA = thiosalicylic acid). Results reveal the six Ln-Au clusters are hierarchical structure that Ln cluster and Au cluster are connected by bifunctional ligands of MPCA or TSA. The excellent “antenna effect” of TSA results in highly luminescence quantum yield of 67% for 6. Interestingly, Ln-Au clusters 4 and 5 show very high MB adsorption capacity of 189 and 158 mg/g in short adsorption equilibrium time of 30 and 5 min, respectively.

Synthesis of two lanthanide clusters LnIII4 (Gd4 and Dy4) with [2 × 2] square grid shape: Magnetocaloric effect and slow magnetic relaxation behaviors

Two isostructural tetranuclear lanthanide clusters named [Ln4(L)4(CH3O)4]·CH3OH (Ln = Gd(III) for 1, Dy(III) for 2, H2L = N′-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl) picolinohydrazide) were successfully isolated by using a polydentate Schiff based ligand and Ln(III) nitrate salts. The structures of 1 and 2 were characterized by X-ray structural analyses, they are held by four double deprotonated ligands L2−. In them all the lanthanide ions are eight-coordinated and distributed over four vertices of a parallelogram, presenting a Ln4 cluster with a strict [2 × 2] square grid pattern. The details of magnetic analysis show that 1 displays weak anti-ferromagnetic exchange between neighboring Gd(III) ions through carboxylate oxygen and methanol oxygen ligand atoms. Furthermore, 1 exhibits significant magnetocaloric effect with the maximum entropy change –ΔSm value of 28.5 J/(kg·K) for ΔH = 7.0 T at 2.0 K. For compound 2, remarkable slow magnetic relaxation behaviors are observed in the presence of zero magnetic field with τ0 = 1.02 × 10−6 s and energy barrier ΔE/kB = 43.24 K.

Induced aggregation and synergistic coordination strategy in metal oxo clusters and their organic frameworks

The new class of materials of metal cluster organic framework (MCOFs) derive from metal organic framework (MOFs) and metal oxo clusters (MOCs). In recent years, MCOFs has attracted considerable attention for their combination of metal oxo clusters and porous characteristics. We herein summarize the progress of lanthanide cluster organic framework (LnCOFs), and point out the induced aggregation and synergetic coordination strategy. This strategy is suitable for making MCOFs and MOCs.

Two Luminescent High-Nuclearity Lanthanide Clusters Ln48 (Ln = Eu and Tb) with a Nanopillar Structure

Two nanosize lanthanide clusters Na3[Eu48O6(OH)84(tca)34(gly)12(H2O)22]2Htca6Cl6H2ONO3 (Eu48) and Na[Tb48O6(OH)84(fca)26(dmp)14(H2O)24]4HfcaNO38Cl (Tb48) have been isolated in presence of th...

An inorganic–organic hybrid material based on a Keggin‐type polyoxometalate@Dysprosium as an effective and green catalyst in the synthesis of 2‐amino‐4H‐chromenes via multicomponent reactions

A novel inorganic–organic hybrid, [Dy4(PDA)4(H2O)11(SiMo12O40)]·7H2O denoted as (POM@Dy‐PDA), based on a lanthanide cluster, a Keggin‐type polyoxomolybdate, and PDA (1,10‐phenanthroline‐2,9‐dicarboxylic acid) was prepared and fully characterized by elemental analysis, Fourier‐transform infrared and UV–Vis spectroscopies, thermogravimetric analysis, powder X‐ray diffraction (PXRD), and single‐crystal X‐ray diffraction. The structural analysis study showed that the [SiMo12O40]4− ions reside in the interspace between two cationic layers as discrete counterions and are not coordinated to the rare‐earth ions. Significantly, this hybrid catalyst is a rare case of an inorganic–organic hybrid polyoxometalate (POM) with a PDA ligand based on CSD search (CSD version 5.40/November2018). The hybrid catalyst was further characterized via powder X‐ray diffraction (PXRD) pattern at room temperature which indicated the good phase purity of the catalyst. BET and Langmuir surface area analysis indicate surface area of POM@Dy‐PDA 6.6 and 51.3 m2g‐1, respectively. The catalytic activity of the hybrid catalyst was successfully examined in the synthesis of 2‐amino‐4H‐chromene derivatives through a multicomponent reaction. A three‐component, one‐pot reaction involving differently substituted benzaldehydes, resorcinol/α‐naphthol/β‐naphthol/4‐hydroxycoumarin/3‐methyl‐4H‐pyrazole‐5(4H)‐one, and malononitrile or ethyl cyanoacetate in the presence of a catalytic quantity of the aforementioned hybrid catalyst in EtOH/H2O under reflux condition gave the corresponding highly functionalized 2‐amino‐4H‐chromenes in satisfactory yields. The catalyst can be reused several times without appreciable loss in its catalytic activity.

Quantum theory of near-field optical imaging with rare-earth atomic clusters

Scanning near-field optical microscopy (SNOM) using local active probes provides general images of the electric part of the photonic local density of states. However, certain atomic clusters can supply more information by simultaneously revealing both the magnetic and the electric local density of states in the optical range. For example, nanoparticles doped with rare-earth elements like europium or terbium provide both electric dipolar (ED) and magnetic dipolar (MD) transitions. In this theoretical paper, we develop a quantum description of active systems (rare-earth ions) coupled to a photonic nanostructure by solving the optical Bloch equations together with Maxwell’s equations. This approach allows us to access the population of the emitting energy levels for all atoms excited by the incident light, degenerated at the extremity of the tip of a near-field optical microscope. We show that it is possible to describe the collected light intensity due to ED and MD transitions in a scanning configuration. By carrying out simulations on different experimentally interesting systems, we demonstrate that our formalism can be of great value for the interpretation of experimental configurations, including various external parameters such as the laser intensity, the polarization and wavelength, the SNOM probe size, and the nature of the sample.

Assembly of Dy60 and Dy30 cage-shaped nanoclusters

Rapid kinetics, complex and diverse reaction intermediates, and difficult screening make the study of assembly mechanisms of high-nuclearity lanthanide clusters challenging. Here, we synthesize a double-cage dysprosium cluster [Dy60(H2L1)24(OAc)71(O)5(OH)3(H2O)27]·6H2O·6CH3OH·7CH3CN (Dy60) by using a multidentate chelate-coordinated diacylhydrazone ligand. Two Dy30 cages are included in the Dy60 structure, which are connected via an OAc− moiety. The core of Dy60 is composed of 8 triangular Dy3 and 12-fold linear Dy3 units. We further change the alkali added in the reaction system and successfully obtain a single cage-shaped cluster [Dy30(H2L1)12(OAc)36(OH)4(H2O)12]·2OH·10H2O·12CH3OH·13CH3CN (Dy30) with a perfect spherical cavity, which could be considered an intermediate in Dy60 formation. Time-dependent, high-resolution electrospray ionization mass spectrometry (HRESI-MS) is used to track the formation of Dy60. A possible self-assembly mechanism is proposed. We track the formation of Dy30 and the six intermediate fragments are screened.

Construction of a heterometallic organic framework based on cuprous-halide clusters and lanthanide clusters with CO2 storage and transformation

A novel 3D porous heterometallic organic framework based on cuprous-halide clusters and lanthanide clusters, [(Cu4I4)2Tb3(NA)9·(H2O)6·(DEF)6]n, was successfully designed and synthesized during the solvothermal synthesis. The as-made sample was analysed by many methods. This material has the preferable stability and CO2 capture capacity, so it can be used as a potential heterogeneous catalyst for the chemical fixation of CO2 and epoxides to generate cyclocarbonates. Furthermore, this MOF can preserve its pristine structure after reusing four times.

Lanthanide clusters as highly efficient catalysts regarding carbon dioxide activation

Lanthanide clusters display a wide substrate scope and high catalytic activity for the insertion of CO2 into epoxides to form cyclic carbonates.

Lanthanoid pyridyl-β-diketonate 'triangles'. New examples of single molecule toroics.

Trinuclear lanthanoid clusters have been synthesised and investigated as toroidal spin systems. A pyridyl functionalised β-diketonate, 1,3-bis(pyridin-2-yl)propane-1,3-dione (o-dppdH) has been used to synthesise a family of clusters of the form [Dy3(OH)2(o-dppd)3Cl2(H2O)4]Cl2·7H2O (1), [Tb3(o-dppd)3(μ3-OH)2(CH3CH2OH)3Cl3][Tb3(o-dppd)3(μ3-OH)2(H2O)(CH3CH2OH)2Cl3]Cl2·H2O (2), [Ho3(OH)2(o-dppd)3Cl(H2O)5]Cl3·3H2O (3) and [Er3(OH)2(o-dppd)3Cl2(H2O)3(CH3OH)]Cl2·3H2O·CH3OH (4). Despite the previous occurrence of this structural motif in the literature, these systems have not been widely investigated in terms of torodic behaviour. Magnetic studies were used to further characterise the complexes. DC susceptibility studies support weak antiferromagnetic exchange in the complexes. Slow magnetic relaxation behaviour is observed in the dynamic AC magnetic studies for complex 1. Theoretical studies predict that complex 1 and 3 have a non-magnetic ground state based on a toroidal arrangement of spins. Changes to the coordination environment in 2 do not support a toroic spin state. The prolate nature of the ErIII centres in complex 4 and large transverse anisotropy do not support the toroidal arrangement of lanthanoid spins in the complex.

Manipulating clusters by regulating N,O chelating ligands: structures and multistep assembly mechanisms

This work is the first study on how changes in ligand chelation sites regulate the assembly and ultimately control lanthanide clusters with different linkages.

Terbium-fluorido cluster: an energy cage for photoluminescence.

We report here that energy migration during luminescence can be extremely minimized by caging the fluorescent centers in a molecular cluster of [Tb6(μ3-F)8(piv)10(Hpiv)4DMF]·xDMF·yH2O 1. Experimental and theoretical simulations reveal that bonding terbium with fluoride is the key to reducing the non-radiative multi-phonon relaxation processes, which is disparate to the common hydroxy-based lanthanide clusters.